Adapter for a power distribution system

ABSTRACT

A male adapter or plug for connecting an electric fixture to a power distribution system of the type providing a substantially continuous convenience outlet enabling adapters to be connected thereto at substantially any selected location along the system. The system includes one or more track components that provide such convenience outlet each of which is equipped with a conductor assembly having a plurality of pairs of conductors extending therealong in insulated relation one from the others. The adapter is operative to mechanically secure an electric fixture to the track component and to electrically connect such fixture selectively to one or another of the pairs of conductors. For this purpose, the adapter comprises support structure releasably interconnectable with the track component, a plurality of pairs of contacts selectively moveable between an inner retracted neutral position and outer extended positions for respective engagement with the pairs of conductors, selector structure movable from a neutral position into one or another of a plurality of operative positions to displace one or another of the pairs of contacts selectively into their outer extended positions, and polarization means for enforcing a predetermined relative orientation upon the track component and adapter so as to relate the operative positions of the selector structure to the respective pairs of conductors provided by the track component.

United States Patent [72] Inventors Larry L. Routh Castro Valley; JamesContratto, Livermore, both of Calif. [211 App]. No. 880,335 [22] FiledNov. 26, 1969 [45] Patented Oct. 12, 1971 [73] Assignee U.S. Industries,Inc.

New York, NY.

[54] ADAPTER FOR A POWER DISTRIBUTION SYSTEM 21 Claims, 10 Drawing Figs.

[52] U.S. Cl 339/21 R, 339/22 B [51] Int. Cl H0lr 9/00 [50] FieldofSearch 339/14, 20-24, 119

[56] References Cited UNITED STATES PATENTS 3,496,518 2/1970 Neumann etal 339/21 3,503,032 3/1970 Routh et al. 339/14 Primary Examiner-MarvinA. Champion Assistant Examiner-Robert A. l-lafer Attorney.loseph B.Gardner ABSTRACT: A male adapter or plug for connecting an electricfixture to a power distribution system of the type providing asubstantially continuous convenience outlet enabling adapters to beconnected thereto at substantially any selected location along thesystem. The system includes one or more track components that providesuch convenience outlet each of which is equipped with a conductorassembly having a plurality of pairs of conductors extending therealongin insulated relation one from the others. The adapter is operative tomechanically secure an electric fixture to the track component and toelectrically connect such fixture selectively to one or another of thepairs of conductors. For this purpose, the adapter comprises supportstructure releasably interconnectable with the track component, aplurality of pairs of contacts selectively moveable between an innerretracted neutral position and outer extended positions for respectiveengagement with the pairs of conductors, selector structure movable froma neutral position into one or another of a plurality of operativepositions to displace one or another of the pairs of contactsselectively into their outer extended positions, and polarization meansfor enforcing a predetermined relative orientation upon the trackcomponent and adapter so as to relate the operative positions of theselector structure to the respective pairs of conductors provided by thetrack component.

PAIENTEUucI 12 Ian SHEET 2 [IF 3 ADAPTER FOR A POWER DISTRIBUTION SYSTEMThis invention relates to a power distribution system and, moreparticularly, to an adapter for mechanically securing an electricfixture to the track component of such power distribution system and forelectrically connecting the fixture to one or another of a plurality ofcircuits provided by the system and track component thereof.

As explained in the copending US. Pat. application of Larry L. Routhentitled Power Distribution System, Ser. No. 696,655, filed Jan. 4,1968, the location of convenience outlets, junction boxes, and otherfixed points of connection within an electric power distribution systemis most often a compromise with the various locations being selected onthe basis of custom or anticipation of the use expected for the buildingspace containing the distribution system. This is particularlyunsatisfactory especially in commercial and industrial buildings sincethe use of any particular space therein is not necessarily static, andany change in use may require relocation of the various outlets andother points of connection. In this respect, the divider walls orpartitions in such buildings may be changed bodily, and modern buildingsare designed so as to afiord ready change of such divider walls from onelocation to another so as to provide considerable versatility in the useof the building space. Also, in many special environments such asmuseums and art galleries in which exhibits are changed periodically,and such as display windows, merchandise showrooms, restaurants, andother public spaces where regular or periodic alteration is intended, areadily changeable lighting placement is advantageous.

In view of this, power distribution systems have been proposedheretofore which are intended to afford a degree of flexibility asrespects the location at which light and other electrically operatedfixtures or devices may be connected thereto, and one such system isdisclosed in the aforesaid US. Pat. application, Ser. No. 695,655. Suchsystem includes one or more track components that provide asubstantially continuous open-mouthed chamber therealong defining aconvenience outlet enabling electric plugs or adapters to be connectedthereto at substantially any selected location; and a typical plug oradapter enabling interconnection of electric fixtures to suchdistribution system is disclosed in the copending US. Pat. applicationof Larry L. Routh and James Contratto entitled adapter for ElectricalPower Distribution Track" Ser. No. 695,597, filed Jan. 4, I968.

The present invention is an improvement over the adapter disclosed insuch copending application Ser. No. 695,597 and has for its objects,among others, the provision of an adapter having a casing formed ofinsulating material so as to protect the user thereof from electricshocks, but at the same time afford a means for grounding any fixtureassociated with the adapter to the track component; an adapter making amechanical connection with the track component to prevent inadvertantloosening which might cause an overhead fixture associated with theadapter to drop free from the track component and injure anyonetherebelow; an adapter having polarizing means such that the adapter canbe connected with the track components in only one predeterminedrelative orientation; and an adapter that provides selective connectionof any lighting or other fixture associated therewith to one or anotherof a plurality of circuits carried by the track component. Additionalobjects and advantages of the invention, especially as concernsparticular features and characteristics thereof, will become apparent asthe specification develops.

A power distribution system and adapter embodying the present inventionmay include one or more elongated, longitudinally extending trackcomponents connected one with another in a succession thereof. Each ofthe track components is relatively rigid and is intended to be supportedalong a ceiling or other building wall, and it is provided with alongitudinally extending open-mouthed chamber defining a substantiallyendless convenience outlet equipped therealong with a conductor assemblyhaving a plurality of pairs of circuit-forming conductors insulated onefrom another. The adapter has an elongated casing at least a portion ofwhich is insertable into the track chamber afier which the adapter ismechanically secured to the track component by support structure carriedby the casing and selectively movable with respect thereto between aretracted position in which the casing can be inserted into andwithdrawn from the chamber and an extended position interlockinglyengaging the track component.

The adapter is also provided with a plurality of pairs of contactsmounted within the casing and movable with respect thereto between innerretracted neutral positions and outer extended operative positions forrespective engagement with the conductors carried by the track componentso as to electrically connect a fixture associated with the adapter toone of the electric circuits. The particular circuit chosen isdetermined by selector structure adjustably carried by the casing formovement with respect thereto from a neutral position in which none ofthe contracts are projected outwardly into their extended position intoone or another of a plurality of operative positions so as to displaceselectively one or another of the pairs of contacts into their outerconductor-engaging extended positions. The adapter also grounds any suchelectric fixture to the track component, thereby protecting the system,adapter and fixture in the event of short circuiting.

An embodiment of the invention is illustrated in the accompanyingdrawings, in which:

FIG. I is a broken perspective view illustrating a portion of aconductor-equipped track component having an adapter secured thereto andthe selector structure of the adapter located in the second of the twooperative positions thereof;

FIG. 2 is a broken vertical sectional view taken along the line 2-2 ofFIG. 1;

FIG. 3 is a vertical sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is a broken longitudinal sectional view taken along the line 4-4of FIG. 1;

FIG. 5 is a broken horizontal sectional view taken along the line 5-5 ofFIG. 4;

FIG. 6 is a transverse sectional view taken along the line 6- 6 of FIG.5 illustrating one pair of contacts in their extended operativepositions;

FIG. 7 is a transverse sectional view taken along the line 7- 7 of FIG.5;

FIG. 8 is a broken vertical sectional view taken along the line 8-8 ofFIG. 7;

FIG. 9 is a broken'horizontal sectional view similar to that of FIG. 5but illustrating the selector structure in its alternate operativeposition; and

FIG. 10 is a transverse sectional view generally similar to that of FIG.6 but showing the selector structure in the altemate operative positionthereof illustrated in FIG. 9 in which another contact pair is in itsouter extended operative position.

The power distribution system partially illustrated in FIG. 1 mayinclude a plurality of interconnected track components 10, only one ofwhich is shown. One or more adapters II are releasably connectable withthe track component 10, and each such adapter is usually associated withan electric fixture or appliance such as an incandescent lightingfixture (not shown). The track component 10 and adapter II are polarizedso as to cause each adapter to have a predetermined orientation withrespect to an associated track component, thereby resulting inparticular polarities to the observed in interconnecting the same. Theparticular polarization means employed will be described in detaillater, and at this point it may be observed that apart from suchpolarization means the track component 10 is generally symmetrical abouta vertical center line therethrough; and in view of such generalsymmetry, the same numerals are employed to identify the oppositelypositioned counterpart elements except that the suffixes a" and b" areadded for purposes of differentiation therebetween.

Accordingly, and referring to FIGS. 2 and 3 in particular, the trackcomponent 10 is seen to include a pair of longitudinally extending andtransversely spaced sidewalls 12a and 12b formed integrally with alongitudinally extending web 14 that is transversely disposed andprojects between the sidewalls intermediate the top and bottom thereof.Adjacent their upper ends, the sidewalls 12 are turned inwardly todefine flanges 15a and 15b that are used in securing the track disclosedin detail in copending US. Pat. application Ser. No.

780,840, entitled Splice Box for a Power Distribution System" filedcontemporaneously herewith.

The track component is provided with a chamber or r receptacle 16 inunderlying relation with the web 14, and such receptacle or chamberdefines a longitudinally extending convenience outlet adapted to receiveone or more of the adapters 11 therein. The chamber 16 adjacent itsupper end in underlying relation with the web 14 is provided with aconductor assembly denoted in general with the numeral 17. The conductorassembly 17 includes an elongated insulator or insulated holder 18having a web 20 of substantially the same general configuration as thatof the track web 14 so as to be able to closely underlie the same, asillustrated in FIGS. 2 and 3. Therefore, the web 20 is also providedwith downwardly inclined segments 21a and 21b respectively correspondingto the downwardly and outwardly inclined segments 22a and 22b of thetrack web E4.

The insulator I8 is provided adjacent the lower outer ends of theinclined sections 21a and 21b with longitudinally extending channelorslot-forming sockets 24a and 24b respectively having conductors 25 and26 mounted therein. Adjacent the upper end of the inclined section 21aat its mergence with the horizontal web section another longitudinallyextending channelor slot-forming socket 27 is provided and has aconductor 28 mounted therein. Each of the conductorequipped slots 24 and27 is provided with a restricted mouth confining the associatedconductor therein and adapted to pass therethrough one of the contactsof the adapter 1 1, as will be explained hereinafter. The conductors 25,26 and 28 may be conventional copper wires (12 gauge, for example), andthey are effectively constrained against longitudinal displacements withrespect to the insulator 18 by the frictional grip of the respectivesockets within which they are confined, thereby eliminating the use ofcollars crimped about the conductors as explained in the aforementionedpending US. Pat. application j Ser. No. 695,655.

The insulator 18 is sufficiently rigid to be substantiallyselfsubstaining and maintain the conductors in the space apartrelationship shown and to confine the same within the slots or channelstherefor. The insulator 18 is also equipped with depending legs 30a and30b respectively extending downwardly substantially parallel with therespectively facing shoulders.

31a and 31b. The legs 30 generally maintain the conductor assembly 17 inthe position or orientation shown but in the absence of the adapter 11,the conductor assembly is free to move downwardly relative to the track10 until the lower extremities of the legs 30 abut the inwardly turnedflanges 32. Such relative dimensions of the legs 30 and spacing betweenthe shoulders 31 and flanges 32 enables the conductor assembly 17 to fitrather loosely within the chamber 16 so that it is freely movable withrespect thereto in longitudinal directions, thereby facilitatingincorporation of the conductor assembly 17 within the track l0.

The receptacle or chamber 16 defining the longitudinally extendingconvenience outlet of the track component 10 is provided withpolarization means, as mentioned hereinbefore, which includes as anelement thereof the asymmetry of the horizontal section of the insulatorweb 20 resulting from the presence of the slot component or socket 27 atone edge thereof but no corresponding component at its opposite edge;and that also includes as another element thereof an upwardly projectingrib or lip 34 along the inner edge of the flange 32b. Such components ofthe polarization means cooperate with the complementary componentsprovided by the adapter 11, as will be described in detail hereinafter.

The conductor assembly 17 provides a plurality of circuits or pairs ofconductors defining the same, and in the particular distribution systembeing considered there are two such circuits and, therefore, two pairsof conductors defining the same. In more particular terms, the conductor26 is common to each of the two circuits and conductor pairs and may beconsidered the neutral conductor. The conductors 25 and 28 areselectively associated with the neutral conductor 26, and the adapter 11in the condition thereof illustrated in FIGS. 3 and 6 has contactsthereof connected with the circuit defined by the conductors 26 and 28,and the adapter in the condition thereof illustrated in FIG. 10 hascontacts thereof connected with the circuit defined by the conductors 26and 25. As is well known, in the usual distribution system the potentialdefined between the neutral conductor 26 and either of the conductors 25and 28 is of the order of l 10 volts AC, and the potential across theconductors 25 and 28 (which potential is not ordinarily used) is of theorder of 220 volts AC.

The adapter 11, as shown best in FIGS. 1 and 4, includes an elongatedcasing having vertically stepped sections 35 and 36 the first of whichprojects downwardly below the lower extremity of the section 36 whichhas a greater longitudinal dimension than the section 35. The casingconsidered as a whole has an upper end portion insertable into thechamber 16 defined by the track component 10, and the casing is adaptedto be releasably secured to the track component by support structureassociated with the casing section 35.

In this respect, such support structure includes a relatively flat plate37 extending generally in longitudinal directions along the bottom wall38 of the casing section 35, and the plate is supported intermediate itsends for pivotal displacements between the full line and broken linepositions illustrated in FIG. 5 which respectively correspond to theaforementioned lock and release positions. Such pivotal movement of theplate '38 is afforded by the mounting therefor which includes a hollowsleeve or tube 40 of cylindrical configuration extending upwardlythrough an opening provided therefor in the bottom wall 38. The plate 37has a central opening passing the sleeve 40 therethrough, and the plateis freely rotatable with respect thereto. The sleeve 40 is confined inposition shown by a pair of nuts 41 and 42 respectively located on theinner and outer sides of the bottom wall 38 and threadedly engaging thesleeve 40. The plate 37 is equipped with a handle 44 extendinglongitudinally from one end thereof through an opening 45 providedtherefor in an end wall 46 of the casing sections 35.

The plate 37 adjacent the opposite ends thereof is equipped withupwardly extending legs 47 and 48 disposed along opposite sides of theplate and turned laterally outwardly at their upper ends to providelocking ears 50 and 51 respectively. As is most evident in FIGS. 2 and4, the cars 50 and 51 are located at slightly different elevations so asto respectively cooperate with the track flanges 32a and 32b and, moreparticularly, so as to accommodate the lip 34 provided along the upperedge of the track flange 32b. Therefore, the car 51 has a slightlyhigher elevation than the ear 50, and they respectively extend throughslots or openings 52 and 54 formed in the up wardly extending sidewall55 and 56 of the casing section 35. At their outer corner portions, theears 50 and 51 are respectively turned downwardly to provide sharpknifelike edges 57 and 58 that are intended to scratch through anyanodizing or other surface coating on the track component 10 along theflanges 32a and lip 34 of the flange 32b so as to make a good electricconnection therewith which is used in grounding any electric fixtureattached by the sleeve 40 to the track component. Evidently, then, thesleeve 40 and plate 37 together with the legs 47 and 48 and ears 50 and51 are metallic conductors, and an electric connection is definedbetween the plate and sleeve in any suitable manner such as via the nut41.

It will be appreciated that when the plate 37 is in the alternateposition thereof shown by broken lines in FIG. 5, the cars 50 and 51 areretracted inwardly to an extent sufficient to free the same from theunderlying flanges 32a and 32b, thereby enabling the adapter 1 l to beinserted into the chambers 16 and removed therefrom. When the ears 50and 51 are in their extended positions, they establish an electricconnection with the track component as previously explained, and theyalso mechanically secure the adapter and any electric fix ture attachedto it, to the track component and thereby support the adapter and suchfixture at a selected location along the track. Thus, the plate 37, legs47 and 48 thereof, and the ears 50 and 51 are sufficiently stiff toafford an excellent support for the adapter and fixture carried therebywhen interlockingly engaging the track flanges 32, as shown in thedrawings.

The casing section 36 is provided with a compartment 60 having aplurality of contacts mounted therein, there being three such contactsin the particular embodiment of the invention being considered and theyare respectively denoted with the numerals 61, 62 and 64 as shown bestin FIGS. 5, 6 and 10. These contacts are adapted to extend outwardlythrough openings provided therefor in the casing section 36 so as toengage the conductors 25 and 26 and 28 as seen in FIGS. 6 and 10. Thecontacts 61 is adapted to engage the neutral conductor 26 and,therefore, is common to the two circuits defined by all of the contactsso that one such circuit is formed by the paired contacts 61 and 64, asshown in FIG. 6, and the other such circuit is formed by the pairedcontacts 61 and 62, as shown in FIG. 10. All of the contacts are adaptedto be positioned concurrently in the inner retracted positions thereof(not shown) in which they are located essentially within the dimensionalconfines of the casing section 36 whereupon the adapter 11 is free to beinserted into the track cavity 16 and withdrawn therefrom.

Further respecting the contact 61, 62 and 64 and the function thereof,it will be noted in FIG. 5 that such contacts are respectively equippedwith (i.e., formed integrally therewith in the embodiment beingconsidered) longitudinally elongated spring legs 65, 66 and 67 which aredisposed entirely within the contact compartment 60 and extend along thelength thereof. The resilient leg 60 is disposed along theaforementioned sidewalls 56 of the adapter and at its rear end it isturned laterally inwardly to form a connector 68 (FIGS. 5 and 7) that isdished downwardly as shown at 70 to provide a generally semicyclindricalrecess adapted to seat the bared end portion of a lead wire 71therealong. The inner extremity of such lead wire 71 is bent downwardlyfor insertion into an opening defined therefor by a boss 72 forming apart of the casing section 36. The lead wire 71 extends rearwardly fromthe connector 70 into the casing section 35 and outwardly therefromthrough the hollow interior of the sleeve 40 for connection to anelectric fixture attached thereto.

Referring to FIG. 8, it will be noted that the connector 68 and concaveprotuberance 70 formed therealong overlies a pair of supports 74 and 75which form the lower jaw of a clamp structure used to mechanicallyconstrain the lead wire 71 in the position shown and to assure a goodelectric connection thereof with the connector 68. Accordingly, theconnector 68 rests upon the jaw supports 74 and 75 and is constrainedthereby against downward movement toward the bottom wall of the casingsection 36. The upper jaw of the clamp structure is formed by a seratedarea 76 on the cover 77 of the casing. The cover 77 is removably securedto the casing sections 35 and 36 by a plurality of longitudinally spacedscrews 78, as shown most clearly in FIG. 4. Whenever the cover is drawndownwardly and into tight juxtaposition with the casing sections, thewire 71 is clamped between the serated jaw 76 and connector 68 of thecontact leg 65, which connector is held finnly in position by the lowerclamping jaw defined by the support 74 and 75.

The resilient leg 66 of the contact 62 also extends rearwardly generallyalong the sidewall 55 of the adapter casing, and the extent to which theleg is biased inwardly from the wall 55 when not displaced outwardlytheretoward by the selector structure to be described hereinafter isclearly evident in FIG. 5 which also shows that the contact 62 isentirely within the outer dimensional limits of the adapter whenretracted so as not to interfere with movement thereof into and out ofthe chamber 16. At its inner end, the leg 66 is turned laterallyinwardly to provide a connector 79 provided with a convex intermediateportion 80 seating a lead wire 81 therein that is turned downwardly soas to extend into a recess provided therefor by a boss 82. The connector79 is supported by spaced-apart supports 84 and 85 forming the lower jawof a clamp the upper jaw of which is defined by serated area 86 alongthe under surface of the cover 77, as heretofore explained. 4

It will be noted in FIG. 7 that the leg 67 of the intermediate contact64 is turned laterally to form a connector 87 that un derlies theconnector 79 so as to be electrically connected therewith. Accordingly,both the contacts 62 and 64 are electrically connected to each otherand, consequently, to the lead wire 81 from any electric fixtureassociated with the adapter 11. It should be observed that the contactleg 67 together with the connector 87 thereof and connector 79 of thecontact leg 66 are all electrically insulated from the connector 68 ofthe contact leg 65 adjacent the serated areas 76 and 86 by a verticalwall 88 extending upwardly from the bottom wall of the casing section 36and seating at its upper end within a channel or recess or 89 providedtherefor in the cover 77.

The selector structure mentioned hereinbefore is denoted in general withthe numeral 90, and it is adjustably carried by the casing section 36for movement with respect thereto from a neutral position (not shown) inwhich all of the contacts 61, 62, and 64 are biased inwardly towardtheir retracted positions by the respectively associated spring legs 65and 66 and 67 into a plurality of operative positions respectively shownin FIGS. 5, 6 and FIGS. 9, 10 so as to displace one or another of thepairs of contacts from their inner retracts positions into their outerextended positions. In the position of the selector 90 illustrated inFIGS. 5 and 6, the contacts 61 and 64 are displaced outwardly intoengagement with the respectively associated conductors 26 and 28 so asto connect any fixture arranged with the adapter 11 to the circuitdefined by such conductors 26 and 28. In the position of the selector 90illustrated in FIGS. 9 and 10, the contacts 61 and 62 are displacedoutwardly so as to engage the conductors 26 and 25 and thereby establishan electric connection with the circuit defined thereby.

The selector structure 90 is in the nature of a cam movable into one oranother of a plurality of positions one of which is an operativeillustrated in FIGS. 1, 5 and 6 wherein the manually movable indicatorlever is pointing to circuit position 02 (FIG. 1) which is denoted bythe indicia 92, another of which is an operative position angularlydisplaced therefrom by a 180 and in which the indicator lever 91 willpoint to circuit position 01 which is denoted by the indicia 94, and theother of which is a neutral position wherein the indicator lever 91 isintermediate the indicia 92 and 94 and points toward the sidewall 56 ofthe adapter or, as viewed in FIG. 1, toward the sidewall 12a of thetrack component 10.

In structural terms, the selector 90 includes a cam 95 having agenerally cylindrical neck 96 seated within a circular opening formed inthe bottom wall 97 of the casing section 36 and rotatable with respectthereto. The cam element 95 is enlarged radially above the neck 96 sothat it cannot move downwardly through the opening in the casing bottomwall. In this respect, the cam element is provided with a radiallyextending cam lobe 98 that is relatively narrow in a vertical directionas is best indicated in FIG. 10, and with a second radially extendingcam lobe 100 diametrally oriented with respect to the lobe 98 and ofconsiderably greater vertical dimension. The indicator lever 91 isformed integrally with the cam element 95 (FIG. 6) and passes downwardlythrough an opening in a retainer plate 101 that underlies the bottomwall 97 of the casing in substantially contiguous relation therewith andis secured to the neck 96 by a plurality of screws or pins 102. Theretainer plate 101 has a greater diameter than that of the neck 96 andopening therefor in the casing bottom wall 97, and therefore constrainsupward movement of the cam element 95 which, as a result, is constrainedagainst bodily displacements relative to the casing but is free to pivotor rotate with respect thereto.

As between FIGS. 6 and 10 it will be observed that the cam lobes 98 and100 are reversely oriented, and it will also be noted in these Figuresthat the resilient legs 65 and 66 of the contacts 61 and 62 havedifferent vertical dimension with the leg 65 projecting downwardly intoclose proximity with the bottom wall 97 of the casing and the leg 66being spaced therefrom by a distance greater than the vertical dimensionof the cam lobe 98. Accordingly, the cam lobe 98 is effective todisplace only the leg 66 and contact 62 outwardly into aconductor-engaging operative position, and this selectivity is evidentin FIG. 6 in which the cam lobe 98 passes freely beneath and underliesthe leg 66. Accordingly, the cam lobe 98 is operative only with respectto the contact 61 and displaces the same into its outer operativeposition whenever the selector structure is in circuit position 02evidenced by the indicator lever 91 pointing to the indicia 92 along thebottom wall 97 of the adaptor. The cam lobe 100, however, because of itsgreater vertical dimension is effective to displace either of thecontacts 61 or 62 outwardly and, therefore, when the indicator lever 91is in the position shown in FIG. 1 in which it is pointing to theindicia 92, the cam lobe 100 is in engagement with the leg 65 anddisplaces the contact 61 outwardly into engagement with the conductor26, as seen in FIG. 6, and when the indicator lever 91 is in itsalternate operative position in which it points to the indicia 94, thecam lobe 100 is in engagement with the resilient leg 66, as shown inFIG. 10, so as to displace the contact 62 outwardly into engagement withthe conductor 25.

Extending upwardly to a considerably greater height than the cam lobe100 is a third cam lobe 104 that in an angular sense is intermediate thecam lobes 94 and 100, as is best seen in FIGS. and 9. The cam lobe 104is operative selectively to engage the leg 97 of the contact 64 anddisplace the contact outwardly to its extended operative positionwhenever the selector structure 90 is in the circuit 02 positionthereof, as shown in FIGS. 5 and 6, but when the selector structure isin its alternate operative position the cam lobe 104 is displaced by 180into the position shown in FIGS. 9 and 10 in which it is remote from thecontact leg 67, thereby enabling the leg and contact to return to theirretracted position. It will be appreciated that when the selectorstructure 90 is in its neutral position, the cam lobe 194 will have beendisplaced in a clockwise direction by 90from the position thereof shownin FIG. 5 and will be remote from the contact leg 67.

The selector structure 90 is confined for angular displacements betweenthe two limiting positions respectively denoted by the indicia 92 and94, as shown in FIG. 1, and the means by which such limits are imposedincludes an arcuate channel or keyway 105 formed in the upper surface ofthe bottom wall 97 of the casing, as shown in FIGS. 4, 5,6,9 and 10.Located within the arcuate channel 105 is a pin or key 106 formedintegrally with the cam element 95 and projecting outwardly from theneck 96, as shown in FIG. 10 and as indicated by broken lines in bothFIGS. 5 and 9. The key or pin 106 is adapted to abut one end of thekeyway or channel 105 to limit angular displacement of the stopstructure in a counterclockwise direction, as viewed in FlG. 5, suchthat the indicator lever 91 points to the indicia 92, and when the stopstructure is displaced in a clockwise direction from the position shownin FIG. 5 into the position illustrated in FIG. 9, the key 106 abuts theopposite end of the channel to position the indicator lever 91 inalignment with the indicia 94.

The polarization means by which a predetermined orientation is enforcedupon the adapter 11 relative to the track component 10 includes tworelated but separate features or means one of which has been describedhereinbefore and is a secondarily effective means including the offsetlip 34 defined along the inner upper edge of the flange 32b and thevertically offset ears 50 and 51 provided by the support structure ofthe adapter. This feature of the polarization means is initially orprimarily becomes effective only after the adapter 11 has the upper endportion thereof inserted into the chamber 16 of the track component 10.The other means or feature comprised by the polarization means isinitially or primarily effective to prevent insertion of the adaptereasing into the chamber 16 unless the adapter has the proper orientationrelative thereto. This initially effective feature will now be describedwith particular reference being given to FIGS. 2, 3, 4 and 7.

Such initially effective polarization feature includes an upwardlyextending projection formed along the casing section 36 including thetop wall 77 thereof, as shown most clearly in FIGS. 2, 3 and 4, and anopen-topped continuation 108 of such projection extending upwardly forthe most part from the casing section 35 but partially from the casingsection 36 in superposed juxtaposition with the aforementioned clampingserations 76 and 86, as seen most clearly in FIGS. 4 and 7. ComparingFIGS. 2 and 3 it will be observed that the extensions 107, 108 areeffective continuations of each other and are in precise axial alignmentbut are offset relative to the center axis or a central vertical planethrough the adapter 1 1. More particularly in this respect, theprojection 107, 108 is closer to the sidewall 56 of the adapter than tothe sidewall 55 thereof and it has sufiicient vertical height so as tosubstantially abut and generally press against the web 20 of theconductor assembly 17.

Cooperative with the combined projection 107, 108 in the sense ofpolarizing the orientation of the adapter I 1 relative to the trackcomponent 10 is the longitudinally extending slotforming socket 27 ofthe conductor assembly 17 which, it will be observed in both FIGS. 2 and3, extends along the projection 107, 108 when the adapter and trackcomponent are properly oriented and united, as shown in the drawings.Assume, however, the case in which the adapter 11 is inadvertentlyrotated 180 relative to the track component 10. In such event, thecorner portion or longitudinally extending upper edge portion 110 of theprojection 107, 108 would underlie the socket 27 and thereby preventcomplete insertion of the adapter into the chamber 16 to enable thesupport structure of the adapter to be displaced into the extendedoperative position thereof in which the ears 50 and 51 interlockinglyengage the flanges 32a and 32b. Thus, in the first instance thepolarization components comprising the offset projection 107, I08 andcomer portion 110 thereof cooperate with the slotforrning socket 27 ofthe conductor assembly 17 to inhibit complete insertion of the adapterinto the chamber 16; and in the second instance the vertical offset ofthe flanges 32a and 32b defined by the upwardly extending lip 34 alongthe latter flange in cooperation with the vertically offset ears 50 and51 of the support structure of the adapter prevent the adapter frombeing mechanically secured to the track component 10 unless the properrelative orientation thereof is observed.

As explained hereinbefore, the conductor assembly 17 fits rather looselyinto the chamber 16, and since the depending legs 30a and 39b of theconductor assembly are somewhat shorter than the vertical distancedefined between the respectively cooperative paired shoulders andunderlying flanges 31a, 32a, and 31b, 32b, the conductor assemblyordinarily assumes a position in which the web 20 thereof is spacedslightly from the overlying web 14 of the track component. However, thevertical dimension of the adapter projection 107, 108 is such that whenthe adapter is properly inserted into the chamber 16 of the trackcomponent, the projection presses against the web 20 and displaces itupwardly toward contiguous juxtaposition with the overlying web 14 ofthe track component, as shown in both H68. 2 and 3. When this occurs,the lower extremities of the legs 30a and 30b are spaced slightly abovethe upper surfaces of the respectively associated flanges 32a and 32b.Such interrelationship of the track component 10, conductor assembly 17and adapter 11 is advantageous in that it properly locates the conductorassembly 17 relative to the adapter 11 between which electric connectionmust be established through the various conductors 25, 26 and 28 and thecontacts 61, 62 and 64 of the adapter thereby obviating any dimensionaldiscrepancies that might otherwise tend to prevent proper alignment ofsuch contacts with the restricted mouths of the various slot-formingsockets defining the entrances to the conductors 25, 26 and 28.

From the foregoing description it will be apparent that adapters 11 maybe readily secured mechanically to the track component 10 atsubstantially any selected location along the continuous convenienceoutlet defined by the chamber 16 simply by orienting the adapter 11properly with respect to the track component and inserting the adapterinto the chamber 16, whereupon the lever or handle 44 can be displacedwithin the limits defined by the slot 55 to extend the ears 50 and 51into overlying juxtaposition with the flanges 32a and 32b, as shownparticularly in FIG. 2. Thereafter, the electric fixture carried by theadapter 11 is connected to the appropriate circuit simply by displacingthe lever 91 from the neutral. position thereof intermediate thecircuit-forming positions respectfully defined by the indicia 92 and 94into either such circuit-forming position as the electric loadconditions may require.

While in the foregoing specification and embodiment of the invention hasbeen described in considerable detail for purposes of making a completedisclosure thereof, it will be apparent to those skilled in the art thatnumerous changes may be made in such details without departing from thespirit and principles of the invention.

What is claimed is:

l. In a power distribution system, the combination of a longitudinallyextending track component comprising a pair of transversely spaced andlongitudinally extending sidewalls and a longitudinally extendingtransverse web fixedly connected with said sidewalls in intermediatedisposition therebetween and defining therewith a longitudinallyextending openmouthed chamber equipped therealong with a conductorassembly having a plurality of pairs of conductors insulated one fromanother; and an adapter for mechanically securing an electric fixture tosaid track component and for electrically connecting such fixtureselectively to one or another of said pairs of conductors; said adaptercomprising an elongated casing having at least a portion thereofinsertable into said chamber, support structure carried by said casingfor selective movement with respect thereto between a retracted positionin which said casing can be inserted into and withdrawn from said trackand an extended position to mechanically secure said adapter thereto, aplurality of pairs of contacts mounted within said casing and each beingmovable with respect thereto between an inner retracted position and anouter extended position for engagement with one of said conductorsfollowing insertion of said casing portion into said chamber, selectorstructure adjustably carried by said casing for movement with respectthereto from a neutral position in which each of said contacts is in itsretracted position into one or another of a plurality of operativepositions so as to displace one pair or another pair of said contactsselectively into their outer extended positions for respectiveengagement with said conductors, and polarization means includingcooperative elements respectively provided by said track component andadapter to enforce a predetermined relative orientation thereon andthereby positively relate the operative positions of said selectorstructure to the respective pairs of conductors provided by said trackcomponent.

2. The power distribution system of claim 1 in which said conductorassembly fits relatively loosely within said track chamber and isdisplaceable toward and away from said track web, and in which saidadapter casing is engageable with said conductor assembly upon insertioninto said chamber to establish the position of said conductor assemblytherein and thereby effect alignment of said conductors with saidcontacts. 3. The power distribution system of claim 2 in which each ofsaid track sidewalls is equipped with a flange extending inwardly intosaid chamber in spaced relation with said track web, and in which saidconductor assembly has depending legs respectively adjacent said tracksidewalls and adapted to rest upon said flanges to limit displacement ofsaid conductor assembly in a direction away from said track web, saidadapter being engageable with said conductor assembly to displace ittoward said track web.

4. The power distribution system of claim 1 in which each of said tracksidewalls is equipped with a flange extending inwardly into said chamberin spaced relation with said track weband providing support surfacesoffset with respect to each other relative to said track web, and inwhich said support structure has offset ears respectively engageablewith said support surfaces and comprising therewith cooperative elementsof the aforesaid polarization means.

5. The power distribution system of claim 1 in which said conductorassembly is provided with a conductor equipped socket extendinglongitudinally along said track chamber in asymmetrical relationtherewith, and in which said adapter casing is provided with anasymmetrical portion located to abut said socket in one orientation ofsaid adapter relative to said track component and to clear said socketin another orientation and comprising with said socket cooperativeelements of the aforesaid polarization means.

6. The power distribution system of claim 5 in which each of said tracksidewalls is equipped with a flange extending inwardly into said chamberin spaced relation with said track web and providing support surfacesofi'set with respect to each other relative to said track web, and inwhich said support structure has offset'ears respectively engageablewith said sup port surfaces and comprising therewith other cooperativeelements of the aforesaid polarization means.

7. The power distribution system of claim 1 in which said supportstructure is located adjacent one end of said casing and said selectorstructure is located adjacent the opposite end thereof, each of saidcontacts having a resilient leg extending to a position intermediate theends of said casing and being equipped thereat with a laterally turnedconnector, and releasable clamp means provided by said casing adjacenteach of said connectors and cooperative with at least certain thereof toconfine a lead wire thereagainst to establish an electric connectiontherebetween.

8. The power distribution system of claim 7 in which said casing isequipped with a removable cover provided with one jaw of the aforesaidclamp means to define the releasability thereof.

9. The power distribution system of claim 1 in which each of said tracksidewalls is equipped with a flange extending inwardly into said chamberin spaced relation with said track web, and in which said supportstructure in the extended position thereof is engageable with saidflanges to mechanically secure said adapter to said track.

10. The power distribution system of claim 1 in which said selectorstructure comprises a cam rotatably supported by said casing for angulardisplacements into the aforesaid neutral and operative positions, meanscarried by said cam and accessible from the exterior of said casing todisplace said cam, and indicia means associated with said casing and camfor indicating the operative positions of said cam.

11. The power distribution system of claim 10 in which said casing isprovided with angularly spaced abutments respectively defining theoperative positions of said cam, and in which said cam is equipped witha stop selectively engageable with said abutments to positively locatesaid cam in the operative positions thereof.

12. The power distribution system of claim 1 in which said conductorassembly fits relatively loosely within said track chamber and isdisplaceable toward and away from said track web, in which said adaptercasing is engageable with said conductor assembly upon insertion intosaid chamber to establish the position of said conductor assemblytherein and thereby effect alignment of said conductors with saidcontacts, in which each of said track sidewalls is equipped with aflange extending inwardly into said chamber in spaced relation with saidtrack web, and in which said support structure in the extended positionthereof is engageable with said flanges to mechanically secure saidadapter to said track.

13. The power distribution system of claim 12 in which said flangesprovide support surfaces offset with respect to each other relative tosaid track web, in which said support structure has oflset earsrespectively engageable with said support surfaces and comprisingtherewith cooperative elements of the aforesaid polarization means, inwhich said conductor assembly is provided with a conductor-equippedsocket extending longitudinally along said track chamber in asymmetricalrelation therewith, and in which said adapter casing is provided with anasymmetrical portion located to abut said socket in one orientation ofsaid adapter relative to said track component and to clear said socketin another orientation and comprising with said socket cooperative otherelements of the aforesaid polarization means.

14. The power distribution system of claim 13 in which said selectorstructure comprises a cam rotatably supported by said casing for angulardisplacements into the aforesaid neutral and operative positions, meanscarried by said cam and accessible from the exterior of said casing todisplace said cam,

indicia means associated with said casing and cam for indicating theoperative positions of said cam, in which casing is provided withangularly spaced abutments respectively defining the operative positionsof said cam, and in which said cam is equipped with a stop selectivelyengageable with said abutments to positively locate said cam in theoperative positions thereof.

15. A longitudinally extending track component for a power distributionsystem, comprising a pair of transversely spaced and longitudinallyextending sidewalls and a longitudinally extending transverse track webfixedly connected with said sidewalls in intermediate dispositiontherebetween and defining therewith a longitudinally extendingopen-mouthed chamber, each of said sidewalls being equipped with aflange extending inwardly into said chamber in spaced relation with saidweb and providing support surfaces offset with respect to each otherrelative to said web, a longitudinally extending conductor assemblyhaving a plurality of pairs of conductors insulated one from another andbeing located within said chamber in loosely fitting relation with saidtrack component and being displaceable with respect thereto toward andaway from said web, said conductor assembly having a longitudinallyextending transverse conductor web corresponding in configuration to theaforesaid track web and extending therealong and having also dependinglegs respectively adjacent said track sidewalls and adapted to rest uponsaid flanges to limit displacement of said conductor assembly in adirection away from said track, said conductor web being engageable byan adapter inserted into said chamber to displace said conductorassembly toward said track web to effect a desired condition ofalignment between said conductor as sembly and such adapter, saidconductor assembly being provided with a pair of symmetrically disposedsockets respectively receiving certain of said conductors therein andextending longitudinally along said chamber on opposite sides thereof,and said conductor assembly also being provided with a further sockethaving another of said conductors mounted therein and extendinglongitudinally along said chamber and projecting inwardly thereinto tomake the same asymmetrical, whereby said asymmetrical socket is adaptedto cooperate with a complementary adapter insertable into said chamberto enforce a predetermined orientation on the adapter relative to saidtrack component togrevent improper electrical connectron of the adapterto sm conductors and said offset support surfaces are adapted tocooperate with correspondingly offset support ears provided by such anadapter to prevent improper mechanical connection thereof to said track.

16. An adapter for mechanically securing an electric fixture to a trackcomponent and for electrically connecting such fixture selectively toone or another of a pair of circuits defined by a plurality ofconductors carried by such track component along a substantiallycontinuous convenience outlet extending longitudinally therealong,comprising an elongated casing having at least a portion thereofinsertable into such outlet, support structure carried by said casingfor selective movement with respect thereto between a retracted positionin which said casing can be inserted into and withdrawn from such outletand an extended position interlockingly engageable with such track tomechanically secure said adapter thereto, a plurality of pairs ofcontacts mounted within said.

casing and each being movable with respect thereto between an innerretracted position and an outer extended position for engagement withone of such conductors following insertion of said casing portion intosuch outlet, selector structure adjustably carried by said casing formovement with respect thereto from a neutral position in which each ofsaid contacts is in its retracted position into one or another of aplurality of operative positions so as to displace one pair or anotherpair of said contacts selectively into their outer extended positionsfor respective engagement with such conductors, and polarization meansincluding elements provided by said adapter to enforce a predeterminedrelative orientation thereon relative to such track component andthereby positively relate the operative positions of said selectorstructure to the respective pairs of conductors provided by such trackcomponent.

17. The adapter of claim 16 in which said selector structure comprises acam rotatably supported by said casing for angular displacements intothe aforesaid neutral and operative positions, means carried by said camand accessible from the exterior or said casing to displace said cam,and indicia means associated with said casing and cam for indicating theoperative positions of said cam.

18. The adapter of claim 17 in which each of said contacts is providedwith a resilient leg extending longitudinally along said casing withinthe interior thereof, said legs having portions thereof disposed atdifferent elevations adjacent said cam, and said cam having a pluralityof cam lobes one of which has an elevation making it cooperative withonly one of said legs, a second of which has an elevation making itcooperative with only a second of said legs, and a third of which has anelevation making it selectively cooperative with said second of saidlegs and a third of said legs, whereby said second leg and the contactassociated therewith are common to each of the operative positions ofsaid cam.

19. The power distribution system of claim 18 in which said casing isprovided with angularly spaced abutments respectively defining theoperative positions of said cam, and in which said cam is equipped witha stop selectively engageable with said abutments to positively locatesaid cam in the operative positions thereof.

20. The power distribution system of claim 19 in which said supportstructure is located adjacent one end of said casing and said selectorstructure is located adjacent the opposite end thereof, each of saidresilient legs extending to a position intermediate the ends of saidcasing and being equipped thereat with a laterally turned connector, andreleasable clamp means provided by said casing adjacent each of saidconnectors and cooperative with at least certain thereof to confine alead wire thereagainst to establish an electric connection therebetween.

21. The power distribution system of claim 20 in which said casing isequipped with a removable cover provided with one jaw of the aforesaidclamp means to define the releasability thereof.

1. In a power distribution system, the combination of a longitudinallyextending track component comprising a pair of transversely spaced andlongitudinally extending sidewalls and a longitudinally extendingtransverse web fixedly connected with said sidewalls in intermediatedisposition therebetween and defining therewith a longitudinallyextending open-mouthed chamber equipped therealong with a conductorassembly having a plurality of pairs of conductors insulated one fromanother; and an adapter for mechanically securing an electric fixture tosaid track component and for electrically connecting such fixtureselectively to one or another of said pairs of conductors; said adaptercomprising an elongated casing having at least a portion thereofinsertable into said chamber, support structure carried by said casingfor selective movement with respect thereto between a rEtracted positionin which said casing can be inserted into and withdrawn from said trackand an extended position to mechanically secure said adapter thereto, aplurality of pairs of contacts mounted within said casing and each beingmovable with respect thereto between an inner retracted position and anouter extended position for engagement with one of said conductorsfollowing insertion of said casing portion into said chamber, selectorstructure adjustably carried by said casing for movement with respectthereto from a neutral position in which each of said contacts is in itsretracted position into one or another of a plurality of operativepositions so as to displace one pair or another pair of said contactsselectively into their outer extended positions for respectiveengagement with said conductors, and polarization means includingcooperative elements respectively provided by said track component andadapter to enforce a predetermined relative orientation thereon andthereby positively relate the operative positions of said selectorstructure to the respective pairs of conductors provided by said trackcomponent.
 2. The power distribution system of claim 1 in which saidconductor assembly fits relatively loosely within said track chamber andis displaceable toward and away from said track web, and in which saidadapter casing is engageable with said conductor assembly upon insertioninto said chamber to establish the position of said conductor assemblytherein and thereby effect alignment of said conductors with saidcontacts.
 3. The power distribution system of claim 2 in which each ofsaid track sidewalls is equipped with a flange extending inwardly intosaid chamber in spaced relation with said track web, and in which saidconductor assembly has depending legs respectively adjacent said tracksidewalls and adapted to rest upon said flanges to limit displacement ofsaid conductor assembly in a direction away from said track web, saidadapter being engageable with said conductor assembly to displace ittoward said track web.
 4. The power distribution system of claim 1 inwhich each of said track sidewalls is equipped with a flange extendinginwardly into said chamber in spaced relation with said track web andproviding support surfaces offset with respect to each other relative tosaid track web, and in which said support structure has offset earsrespectively engageable with said support surfaces and comprisingtherewith cooperative elements of the aforesaid polarization means. 5.The power distribution system of claim 1 in which said conductorassembly is provided with a conductor equipped socket extendinglongitudinally along said track chamber in asymmetrical relationtherewith, and in which said adapter casing is provided with anasymmetrical portion located to abut said socket in one orientation ofsaid adapter relative to said track component and to clear said socketin another orientation and comprising with said socket cooperativeelements of the aforesaid polarization means.
 6. The power distributionsystem of claim 5 in which each of said track sidewalls is equipped witha flange extending inwardly into said chamber in spaced relation withsaid track web and providing support surfaces offset with respect toeach other relative to said track web, and in which said supportstructure has offset ears respectively engageable with said supportsurfaces and comprising therewith other cooperative elements of theaforesaid polarization means.
 7. The power distribution system of claim1 in which said support structure is located adjacent one end of saidcasing and said selector structure is located adjacent the opposite endthereof, each of said contacts having a resilient leg extending to aposition intermediate the ends of said casing and being equipped thereatwith a laterally turned connector, and releasable clamp means providedby said casing adjacent each of said connectors and cooperative with atleast certain thereof to confine a lead wIre thereagainst to establishan electric connection therebetween.
 8. The power distribution system ofclaim 7 in which said casing is equipped with a removable cover providedwith one jaw of the aforesaid clamp means to define the releasabilitythereof.
 9. The power distribution system of claim 1 in which each ofsaid track sidewalls is equipped with a flange extending inwardly intosaid chamber in spaced relation with said track web, and in which saidsupport structure in the extended position thereof is engageable withsaid flanges to mechanically secure said adapter to said track.
 10. Thepower distribution system of claim 1 in which said selector structurecomprises a cam rotatably supported by said casing for angulardisplacements into the aforesaid neutral and operative positions, meanscarried by said cam and accessible from the exterior of said casing todisplace said cam, and indicia means associated with said casing and camfor indicating the operative positions of said cam.
 11. The powerdistribution system of claim 10 in which said casing is provided withangularly spaced abutments respectively defining the operative positionsof said cam, and in which said cam is equipped with a stop selectivelyengageable with said abutments to positively locate said cam in theoperative positions thereof.
 12. The power distribution system of claim1 in which said conductor assembly fits relatively loosely within saidtrack chamber and is displaceable toward and away from said track web,in which said adapter casing is engageable with said conductor assemblyupon insertion into said chamber to establish the position of saidconductor assembly therein and thereby effect alignment of saidconductors with said contacts, in which each of said track sidewalls isequipped with a flange extending inwardly into said chamber in spacedrelation with said track web, and in which said support structure in theextended position thereof is engageable with said flanges tomechanically secure said adapter to said track.
 13. The powerdistribution system of claim 12 in which said flanges provide supportsurfaces offset with respect to each other relative to said track web,in which said support structure has offset ears respectively engageablewith said support surfaces and comprising therewith cooperative elementsof the aforesaid polarization means, in which said conductor assembly isprovided with a conductor-equipped socket extending longitudinally alongsaid track chamber in asymmetrical relation therewith, and in which saidadapter casing is provided with an asymmetrical portion located to abutsaid socket in one orientation of said adapter relative to said trackcomponent and to clear said socket in another orientation and comprisingwith said socket cooperative other elements of the aforesaidpolarization means.
 14. The power distribution system of claim 13 inwhich said selector structure comprises a cam rotatably supported bysaid casing for angular displacements into the aforesaid neutral andoperative positions, means carried by said cam and accessible from theexterior of said casing to displace said cam, indicia means associatedwith said casing and cam for indicating the operative positions of saidcam, in which casing is provided with angularly spaced abutmentsrespectively defining the operative positions of said cam, and in whichsaid cam is equipped with a stop selectively engageable with saidabutments to positively locate said cam in the operative positionsthereof.
 15. A longitudinally extending track component for a powerdistribution system, comprising a pair of transversely spaced andlongitudinally extending sidewalls and a longitudinally extendingtransverse track web fixedly connected with said sidewalls inintermediate disposition therebetween and defining therewith alongitudinally extending open-mouthed chamber, each of said sidewallsbeing equipped with a flange extending inwardly into said chamber inspaced relation with said web and proViding support surfaces offset withrespect to each other relative to said web, a longitudinally extendingconductor assembly having a plurality of pairs of conductors insulatedone from another and being located within said chamber in looselyfitting relation with said track component and being displaceable withrespect thereto toward and away from said web, said conductor assemblyhaving a longitudinally extending transverse conductor web correspondingin configuration to the aforesaid track web and extending therealong andhaving also depending legs respectively adjacent said track sidewallsand adapted to rest upon said flanges to limit displacement of saidconductor assembly in a direction away from said track, said conductorweb being engageable by an adapter inserted into said chamber todisplace said conductor assembly toward said track web to effect adesired condition of alignment between said conductor assembly and suchadapter, said conductor assembly being provided with a pair ofsymmetrically disposed sockets respectively receiving certain of saidconductors therein and extending longitudinally along said chamber onopposite sides thereof, and said conductor assembly also being providedwith a further socket having another of said conductors mounted thereinand extending longitudinally along said chamber and projecting inwardlythereinto to make the same asymmetrical, whereby said asymmetricalsocket is adapted to cooperate with a complementary adapter insertableinto said chamber to enforce a predetermined orientation on the adapterrelative to said track component to prevent improper electricalconnection of the adapter to said conductors and said offset supportsurfaces are adapted to cooperate with correspondingly offset supportears provided by such an adapter to prevent improper mechanicalconnection thereof to said track.
 16. An adapter for mechanicallysecuring an electric fixture to a track component and for electricallyconnecting such fixture selectively to one or another of a pair ofcircuits defined by a plurality of conductors carried by such trackcomponent along a substantially continuous convenience outlet extendinglongitudinally therealong, comprising an elongated casing having atleast a portion thereof insertable into such outlet, support structurecarried by said casing for selective movement with respect theretobetween a retracted position in which said casing can be inserted intoand withdrawn from such outlet and an extended position interlockinglyengageable with such track to mechanically secure said adapter thereto,a plurality of pairs of contacts mounted within said casing and eachbeing movable with respect thereto between an inner retracted positionand an outer extended position for engagement with one of suchconductors following insertion of said casing portion into such outlet,selector structure adjustably carried by said casing for movement withrespect thereto from a neutral position in which each of said contactsis in its retracted position into one or another of a plurality ofoperative positions so as to displace one pair or another pair of saidcontacts selectively into their outer extended positions for respectiveengagement with such conductors, and polarization means includingelements provided by said adapter to enforce a predetermined relativeorientation thereon relative to such track component and therebypositively relate the operative positions of said selector structure tothe respective pairs of conductors provided by such track component. 17.The adapter of claim 16 in which said selector structure comprises a camrotatably supported by said casing for angular displacements into theaforesaid neutral and operative positions, means carried by said cam andaccessible from the exterior or said casing to displace said cam, andindicia means associated with said casing and cam for indicating theoperative positions of said cam.
 18. The adapter of claim 17 in whicheach of said contacts is provided with a reSilient leg extendinglongitudinally along said casing within the interior thereof, said legshaving portions thereof disposed at different elevations adjacent saidcam, and said cam having a plurality of cam lobes one of which has anelevation making it cooperative with only one of said legs, a second ofwhich has an elevation making it cooperative with only a second of saidlegs, and a third of which has an elevation making it selectivelycooperative with said second of said legs and a third of said legs,whereby said second leg and the contact associated therewith are commonto each of the operative positions of said cam.
 19. The powerdistribution system of claim 18 in which said casing is provided withangularly spaced abutments respectively defining the operative positionsof said cam, and in which said cam is equipped with a stop selectivelyengageable with said abutments to positively locate said cam in theoperative positions thereof.
 20. The power distribution system of claim19 in which said support structure is located adjacent one end of saidcasing and said selector structure is located adjacent the opposite endthereof, each of said resilient legs extending to a positionintermediate the ends of said casing and being equipped thereat with alaterally turned connector, and releasable clamp means provided by saidcasing adjacent each of said connectors and cooperative with at leastcertain thereof to confine a lead wire thereagainst to establish anelectric connection therebetween.
 21. The power distribution system ofclaim 20 in which said casing is equipped with a removable coverprovided with one jaw of the aforesaid clamp means to define thereleasability thereof.